The finding could mean that children who bang their heads may not need to undergo radiation-exposing scans to determine if they have suffered a brain lesion.

Researchers from Orlando Health in Florida detected a biomarker released by the brain during injury.

They found that the biomarker can stay in the bloodstream for up to a week - which means patients who suffer delayed symptoms of concussion could easily be identified.

"Symptoms of a concussion, or a mild to moderate traumatic brain injury, can be subtle and are often delayed, in many cases by several days," said Dr Linda Papa, lead author of the study.

"This could provide doctors with an important tool for ­simply and accurately ­diagnosing those patients, ­particularly children, and making sure they are treated properly.

"This test could take the guesswork out of making a diagnosis by allowing doctors to simply look for a specific biomarker in the blood."

The new study shows that when an injury occurs to the brain, a biomarker - the glial fibrillary acidic protein - is released. The biomarker enters the bloodstream which means it can be detected with a simple blood test.

Researchers analysed nearly 600 patients for three years and found the blood test was able to detect mild to moderate traumatic brain lesions with up to 97pc accuracy in adults.